Astronomers are correct that the “black hole closest to us” does not exist

outer space

Technology Innovation Website Editor – 02/03/2022

HR 6819, which was previously thought to be a triple system with a black hole, is actually a two star system without a black hole.
[Imagem: ESO/L. Calada]

The black hole that wasn’t

In 2020, a team led by astronomers from the European Southern Observatory (ESO) announced The discovery of the closest black hole to Earthonly 1,000 light-years away, in the HR 6819 system.

However, this finding has been challenged by other groups of researchers, including an international team based at the Catholic University of Leuven, Belgium.

In a paper published today, the Belgian team joined forces with the team that originally announced the discovery to announce that, in fact, there is no black hole in HR 6819. Instead, what is a two-star “vampire” system is a rarity. It is a short-lived stage of its development.

Two interpretations of the same data

At first, Thomas Rivinius and his colleagues were convinced that the best explanation for their data was that HR 6819 was a triple system, with one star orbiting a black hole every 40 days, and a second in a much wider orbit. far.

However, a study led by Julia Bodensteiner, then a doctoral student at the University of Leuven, suggested a different explanation for the same data: HR 6819 could also be a system with only two stars in a 40-day orbit and no black holes. This alternative scenario would require that one of the stars be “undressed”, that is, at an early stage it lost a significant part of its mass in favor of the other star.

Professor Abigail Frost, who led the data comparison, said: “We have reached the limit of the existing data, so we had to switch to a different monitoring strategy to decide between the two scenarios proposed by the two teams.”

To make matters clear, the two teams worked together to obtain new and clearer data using the VLT Interferometer (VLTI) and the VLT telescope itself. “VLTI was the only infrastructure that would give us the critical data we needed to distinguish between the two scenarios,” said Dietrich Bade, author of the original and current study.

“We agreed that there were two light sources in the system, so the question was whether they would orbit each other in close orbits, as in the “naked” star scenario, or, conversely, would they be far from each other, as in the black hole scenario ‘” explained Rivinius.

stellar vampire

To distinguish between the two hypotheses, the astronomers used the GRAVITY instruments installed on the VLTI and MUSE (multi-unit spectrophotometer) from VLT.

“MUSE confirmed that there is no bright companion in a farther orbit, while GRAVITY’s spatial resolution was able to distinguish two bright sources separated by only a third of the distance between the Earth and the Sun,” Frost said. “This data proved to be the final piece of the puzzle and allowed us to conclude that HR 6819 is a binary system without a black hole.”

“Our best explanation so far is that we are observing this binary system shortly after a star has ‘sucked up’ the atmosphere from its companion star. This is a common phenomenon in nearby binary systems referred to as a ‘stellar vampire,’” Bodensteiner explained. The same time that the donor star found itself ‘striped’ of some of its material, the receiving star began to rotate more rapidly.”

“Monitoring this post-reaction phase is very difficult, because its duration is very short,” Frost adds. “This is what makes our discovery so interesting, as it presents us with an ideal candidate for studying how this type of vampire affects the evolution of massive stars, and thus the formation of associated phenomena, including gravitational waves and violent supernova explosions.”

When searching for black holes, the team remains optimistic, saying it’s only a matter of time before astronomers find them.

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